We study monolayer WSe2 using ultrafast electron diffraction. We introduce an approach to quantitatively extract atomic-site-specific information, providing an element-specific view of incoherent atomic vibrations following femtosecond excitation. Via differences between W and Se vibrations, we identify stages in the nonthermal evolution of the lattice. Combined with a calculated phonon dispersion, this element specificity enables us to identify a long-lasting overpopulation of specific optical phonons, and to interpret the stages as energy transfer processes between specific phonon groups. These results demonstrate the appeal of resolving element-specific vibrational information in the ultrafast time domain.
@article{arxiv.2405.17099,
title = {Element-specific ultrafast lattice dynamics in monolayer WSe2},
author = {H. Jung and S. Dong and D. Zahn and T. Vasileiadis and H. Seiler and R. Schneider and S. Michaelis de Vasconcellos and V. C. A. Taylor and R. Bratschitsch and R. Ernstorfer and Y. W. Windsor},
journal= {arXiv preprint arXiv:2405.17099},
year = {2024}
}